Color selection electrode mount with coating of ductile metal

ABSTRACT

In a color television display tube, a suspension device for a color selection electrode, comprising suspension members secured to said electrode and resilient metal clamping members adapted for being clamped in a recess in the glass envelope of the tube. At the area where the clamping member contacts the wall of the recess, a layer of ductile metal or rounded studs are provided on the clamping member to prevent surface damages of the glass wall during assembly.

Unit States Pate Bakker et al.

1 1 Nov. 18, 1975 COLOR SELECTION ELECTRODE MOUNT WITH COATING OF DUCTILE METAL [75] Inventors: Gijsbertus Bakker; Johannes Henricus Nicolaas Gijrath, both of Eindhoven, Netherlands [73] Assignee: U.S. Philips Corporation, New

York, NY.

[22] Filed: May 30, 1974 [21] Appl. No.: 474,586

[30] Foreign Application Priority Data June 14, 1973 Netherlands 7308243 [52] US. Cl 313/404; 313/482 [51] Int. CL. ..I-I01J 29/02; H01J 29/07; H01J 31/20 [58] Field of Search 313/404, 406, 405, 407, 313/408, 402

[56] References Cited UNITED STATES PATENTS 2,951,167 8/1960 Kegg et a1 313/406 3,335,479 8/1967 Morrell 313/406 X 3,524,971 8/1970 Schwartz et al. 313/406 3.548.235 12/1970 Driedijk et a1 313/404 Primary ExaminerRobert Sega] Att0rne Agent, or Firm-Frank R. Trifari; George B. Berka [57] ABSTRACT In a color television display tube, a suspension device for a color selection electrode, comprising suspension members secured to said electrode and resilient metal clamping members adapted for being clamped in a recess in the glass envelope of the tube. At the area where the clamping member contacts the wall of the recess, a layer of ductile metal or rounded studs are provided on the clamping member to prevent surface damages of the glass wall during assembly.

5 Claims, 4 Drawing Figures U.S.'Patent Nov. 18,1975, Sheet1of2 3,921,024

Fig.1

Sheet 2 0f 2 US. Patent Nov. 18, 1975 COLOR SELECTION ELECTRODE MOUNT WITH COATING OF DUCTILE METAL The invention relates to a color television display tube having a color selection electrode, in particular a shadow mask, and a suspension device for suspending said color selection electrode within the envelope, in particular within the cup-shaped glass window of the tube, which suspension device consists mainly of suspension members which are connected to the said electrode and which each comprise a clamping member manufactured from a resilient material, said clamping member being clamped in a recess present in the envelope of the tube,

A color television display tube having such a suspension device for the shadow mask is known from the US. Pat. No. 3,548,235. The suspension device described in the said patent specification consists of striplike suspension members which are secured to the four comers of a substantially rectangular shadow mask. The free end of each suspension member is connected to the central portion of an omega-shaped resilient strip which latter is clamped in a recess present in the glass of the upright edge of the window. Said omega-shaped strip which forms the above-mentioned clamping member contacts the wall of the recess on either side of the said central portion in at least three places in such manner that a tilt-free clamping connection between the clamping member and the upright edge of the window is obtained. It has been found, however, that just in those places where the clamping member presses against the wall of the recess, the envelope of the tube is less resistant to the influences of large temperature changes. In the connection process of cone and window usual for said tubes and also during the degassing of the tube, the windows of an inadmissibly high number of tubes crack during the heating of the tube. It has been found that said crack in the window always finds its origin at or near the said contact points of clamping member and recess. The use of a less stiff spring as a clamping member so as to reduce the pressure forces on said contact points on the one hand provided a slight improvement but on the other hand resulted in a decrease of the resistance to shocks of the clamping joint and therefore this was less desired.

It has been found, however, that the cracking of the window can be avoided also when using stiff springs if, according to the invention, means are provided at least at the area where the clamping member contacts the wall of the recess which means counteract the occurrence of surface damages of said wall in cooperation with the clamping member.

The invention is based on the recognition obtained from examinations that the occurrence of cracks in the window is not in the first place a result of the forces which are exerted in the static condition on the wall of the recess by the clamping member but is rather formed as a result of surface damages of said wall and in particular by scratches formed therein. Said surface damages occur mainly when the clamping members are cess the formation of scratches on the walls of the recesses is difficult to avoid, in particular because upon removing or inserting the mask all the clamping members have simultaneously to be inserted and removed, respectively, from the recesses. The results of such surface damages prove to be disastrous when in a later stage of the manufacture the tube is heated in a furnace at a comparatively high temperature. Since in general the thermal energy will penetrate from the outside into the envelope of the tube, said envelope will initially expand more on the outside than on the inside. As a result of this the inside of the envelope is subjected to tensile stress in which a very unfavourable stress distribution occurs at the area where the inner wall of said envelope changes into a recess. Said stresses easily result in cracking at the area of scratches present in the wall of the recess, while in addition the pressure forces exerted or the wall of the recess. Such a layer is preferably proplaced in their recesses or are removed therefrom.

Upon providing the various phosphor layers on the inside of the display screen, the shadow mask in the conventional photographic method is used as a negative for each layer individually during exposing said phosphor layer. This means that the mask and hence also the clamping members should be inserted and removed from the window at least three times. During said provided on the clamping member since it has been found that, upon inserting, said clamping member always scratches along the wall of the recess in substantially the same places. A coating provided on the wall at that area would therefore soon be removed or at least have lost its protective action.

If, as is known from the said US. patent specification, the clamping member consists of a bent metal strip, the sharp edge of the side of the strip facing the wall of the recess may scratch along said wall so that damages may still occur due to an inclined position occurred during the insertion or removal of the clamping member. According to the invention this is avoided if near said sharp edges the strip has rounded studs. Said studs also form readily defined places for engagement for the clamping member. If desired, said studs may have a layer of a ductile metal, but this is not strictly necessary since, as will become apparent hereinafter, the forces exerted by the clamping member on the wall are distributed between at least two studs. A combination of the said means is preferably used in which the strip in certain pressure places has a rounded stud and in other pressure places is covered only with a layer of a ductile metal.

The invention will be described in greater detail with reference to a drawing, in which:

FIG. 1 shows a color television display tube according to the invention having a suspension device for the colour selection electrode,

FIG. 2 is a perspective diagram on an enlarged scale of a suspension of the color selection electrode in a corner of the window shown diagrammatically in FIG. 1,

FIG. 3 is a perspective view of the suspension member shown in FIG. 2, and

FIG. 4 shows another embodiment of a suspension member.

FIG. 1 shows a color television display tube the envelope of which consists of a cup-shaped window 1, a conical part 2 and a neck 3. A mosaic pattern 5 composed of groups of three phosphors luminescing in the colors red, green and blue is provided on the inside of the display screen 4 by means of a photographic process. The tube furthermore comprises a shadow mask 6 which is suspended in the corners of the substantially rectangular window 1 by means of suspension members 7 each having a clamping member 8. The suspension member 7 is approximately at right angles to the electron beam 10 which originates from an electron gun I1 and is deflected towards the corners of the shadow mask by means of the deflection coil 9.

The suspension device by means of which the mask 6 is secured in the cup-shaped window 1 will be described in greater detail with reference to FIGS. 2 and 3, in which latter figure the suspension member as such is shown again from another point of view. The upright edge 12 of the window 1 has a thickening 13 in the corners in which a cupboard-like recess 14 is present which extends over the corner point. Said recess is bounded by a bottom surface 27 formed by the upright edge of the window, two side surfaces 22 and two fitting surfaces 21. The depth of said recess is approximately three mms and the corners thereof have a radius of rounding of approximately 1 mm. Said recesses are moulded in the upright edge during the moulding of the window. The shadow mask 6 has an upright edge 15 and is reinforced in the corners by means of a supporting strip 16 welded on the inside of said upright edge. Said strip comprises a bent edge 17 on which one end of the suspension member 7 is welded. The other end of the suspension member forms one assembly with the clamping member 8 consisting of a chromium-iron strip which is bent at the ends with a radius of curvature of approximately 1.5 mms. Two tensioning members 18 are furthermore welded to the strip-like clamping member. By pinching said tensioning members towards each other, the clamping member 8 is tensioned like a bow, in which condition said member can be inserted into the recess 14 with a small amount of play. The clamping member at the bent ends slightly tapers towards the lower edge 19. Said lower edge has two lugs 20 with which the clamping member bears on the fitting surfaces 21 of the recess 14. When the clamping member is inserted into the recess, the walls of the recess and in particular the sides 22 can easily be damaged. This is the case also when the clamping member sets after releasing the tensioning members 18. In order to prevent the formation of said damages, the clamping member near the bent ends is covered with an aluminium layer 23. Said layer can be provided on the clamping member in a simple manner by the Schoop process (by spraying).

When the clamping member has been provided in its place in the recess, it presses on either side of the central portion thereof in at least three places against the walls of the recess. In FIGS. 2 and 3 said places on the clamping member are denoted by 24, 25 and 25'. The pressure places 24 are situated approximately halfway the width of the strip in the ends thereof which are bent back and are covered with aluminium. The pressure points 24' on the sides 22 of the recess correspond to the pressure places 24. The pressure places 25 and 25' are defined by rounded studs present near the lower edge 19 and the upper edge 26 of the strip. These studs are formed by a local boss of said strips and also prevent the sharp edges 19 and 26 from scraping along the wall of the recess when the clamping member assumes a slightly inclined position upon being inserted or removed. The pressure forces exerted on the wall by the studs 25 and 25' are substantially equally large and approximately equal to half the force which is exerted on said wall by the clamping member at 24. Covering said studs with a layer of aluminum has therefore not proved necessary.

Another embodiment of the clamping member is shown in FIG. 4. The tensioning members 38 form one assembly with the clamping member 31, while the suspension member 37 is welded or riveted to the clamping member. In such a construction, for example, the suspension member may be manufactured from a material different from the clamping member. The clamping member, like the above-described clamping member, is covered with a layer of aluminum 33 of 0.05 mm thickness and furthermore shows near the upper and lower edges, on either side of the central portion, rounded studs 35 and 35'.

What is claimed is:

1. A color television display tube having a cupshaped glass window including a plurality of recessed portions in its inner side wall, a color selection electrode, a plurality of elongate suspension members of resilient material, one end of each suspension member being secured to the selection electrode and the projecting opposite end thereof being provded with a transverse clamping member of a resilient metal, each clamping member having contact surfaces abutting against the facing sides surfaces of the assigned recessed portion and a layer of a ductile metal deposited between said resilient metal contact surfaces and said glass side surfaces.

2. A color television display tube as claimed in claim 1 wherein each clamping member is provided with rounded projections abutting against the bottom wall of the corresponding recessed portion.

3. A color television display tube as claimed in claim 2 wherein the projections are embossed parts of the clamping member.

4. A color television display tube as claimed in claim 1, wherein said ductile metal is aluminum.

5. A color television display tube as claimed in claim 1, wherein the layer of ductile metal is provided on the clamping member. 

1. A color television display tube having a cup-shaped glass window including a plurality of recessed portions in its inner side wall, a color selection electrode, a plurality of elongate suspension members of resilient material, one end of each suspension member being secured to the selection electrode and the projecting opposite end thereof being provded with a transverse clamping member of a resilient metal, each clamping member having contact surfaces abutting against the facing sides surfaces of the assigned recessed portion and a layer of a ductile metal deposited between said resilient metal contact surfaces and said glass side surfaces.
 2. A color television display tube as claimed in claim 1 wherein each clamping member is provided with rounded projections abutting against the bottom wall of the corresponding recessed portion.
 3. A color television display tube as claimed in claim 2 wherein the projections are embossed parts of the clamping member.
 4. A color television display tube as claimed in claim 1, wherein said ductile metal is aluminum.
 5. A color television display tube as claimed in claim 1, wherein the layer of ductile metal is provided on the clamping member. 